A p-n junction is a semiconductor that is made up of p-type material on one side and n-type material on the other. This device shows some very interesting (and useful) electronic behavior that is critical to solar cell function. This section will take a look at the physics of the p-n junction, beginning with a study of the device in the open-circuit case (that is, isolated from any circuits or external fields), and continuing on to a study of the properties that arise when the device is placed in a circuit and a voltage is applied.
Top: A schematic of p-n junction with an applied voltage.Bottom: The circuit symbol for the p-n junction. Image courtesy of Wikimedia Commons.